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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b136f0fad14b7dfbf38045f8ead87db8fdc8b78add2b5b198b9e0f6a02c98342' 
  AND token = 'l48iiAYbpQIAPxWTwelUO9P7tI176rAktEOcoadi/Zc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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