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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '86b4e81bfffd7edee08944575a7c1555dc902e7717d04417d735dbb99dd4acb0' 
  AND token = '51EkhPut1EFSUMwB9UVj75aYmPiQHEelSQSnn136V4Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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