SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51200f8234a21316aa81c95a5d82f6be8e132b38d39b5da7a00c8f5d0642e1f7' 
  AND token = 'YxJgvfClfuPjrVpFUU1bPNzLgVIY8lKN1bAc2BH6i5w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

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