SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b21e50572beece47a6ee9233de2c978aace8e411768d2d40e37dbba1174bf53d' 
  AND token = 'ivA+u2ksXm6PZGkjlP7Gb8E+Qkjpr9Ls79kJNm4yYck=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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