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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f6ca9db3dcaa03aa1d3c7f07454a18244cd9abe256c63dd3baa0534a68c2018a' 
  AND token = 'KQQOeXnmkZqdYMv/SlelkhiTe8rKk7NQ8VJ0q8tAM+I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}