SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '375db8f1a97d143e48580d01b7631df2c7d209b18936be29fbc90062cabcf889' 
  AND token = 'ndm3tM3+cYkoRZjpcqJ/fM76EKxhGHIvXdYTZRBsvnM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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