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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4919721022f7802007b38ad0dba45e6ded0fe08764b1cbaa6e9eddd5199957a' 
  AND token = 'b8uNQ4w8aGGQwdKhMNYORtS/HVZ0k80ysXQPHs2Eu10=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}