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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8912dc2f79653d80c6c9c3b451771d86f6f8c0d9a86b113c00d13b6e3d0bee8a' 
  AND token = 'vSALTy3vU6R4YUPjN+vH3k3PNW8qEDeitjYiHkUCgFk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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