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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4e38629e253abf1d3c60974947de4def399f15b48d0681359e3d34a5eefeecbb' 
  AND token = '+EDeSeYyBcpwKxaAP/DQMXwFej9MvedXnExJB9dc0nc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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