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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f8f9a25ff987dcb834ce264c10db9a88e30951afc8d9ad47594e51daa644a30' 
  AND token = 'mb2it/TUNCim1PJyfQ/epM/KRQ1Cg7X1T5t5FSgOLD0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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