SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6819192f9b7e0444f3cdf864e327881f690473218afe188dfe1b4fb0182eaa9c' 
  AND token = '9pUrz/JpLvhweGS3ZgNL7BWCM1Y9hKwXjfPwfewPhIM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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