SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ec21cd65b636487c0dd8924a3b027f566f923893e6a6585557192dc2d976f446' 
  AND token = 'nZAMKzlnmDLmrE2qL2NgDT8GMR4VBrTY35OSgtS/yDo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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