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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4142bb78624fd23ab4bc7fca88e9a947976aacdcb3e1a1b5c1a5506cba62257' 
  AND token = 'Oj/Sd4rKwKiYOGmNtasSMmKt2BjMWoolAAMCAI3DTZI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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