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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '27275d2053f3d91fe3636769cb4a92e102a6c7296d9ade1249ad2ed014f34e27' 
  AND token = '7HbJwTWNQ80uHSWIMRJOPPXVvuZsEjER+oFMdnREbqM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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