SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f26af886fead58ee661c40a144186c2bf3136baf94b7939b8b5686ef9279a875' 
  AND token = 'RRP8ddjeUN6p16HAu4LP6CGZMJAoNinAQcMtNMcLwO0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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