SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8e340bd3118d0156116c36855af6fb882564e0b03eadd91d5b4250010104ba9' 
  AND token = 'Q9/1+sY54GtSTyRHJTWFvRTkBY5rEPgf2IWymRUCnxg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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