SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7c786a572825af80977bfbe3d5d266da819009c2e300dda9d1503cd152841b2a' 
  AND token = 'nsRvnXTBGERrSepcsPCLbwPu4E00ce6NcMlJSxLU/Fk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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