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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd7936950b2dd3c00f1778feb9ad5001fd0bcd63970a4adbdba921c0208cbb738' 
  AND token = 'RnheCHWWD8ItGaQSCy/2v2JqFdqOTyrdepgCvz2yBmY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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