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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4478e693d1db6993560587b471e48a18962580e1a85fffd002e55c4a316ea81' 
  AND token = 'h5j/mAEJvlB6Ilajiwf5jK8Xl1/OZ+aV/hlf8NWFuI4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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