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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '20b0bdc6c256672a9e6a716366dbebcd0036f4d0ce0454194c395d3594b39b6b' 
  AND token = '5mWbAMs3GVmRpQ/JWzZSeQv2L7/8AhZ818DxNIPmrBg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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