SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1c790891660533aec4acc0269bb50bc8d70ff085af2e4333e96447a0f0928290' 
  AND token = '7/uQ6k9Yal9i6grXYqdN0/BIB4/bUWdEJFGThux6hr4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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