SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c2c889ba5203b45a637314800accd029b51526a9704df1fe654d4cbe0b71afcd' 
  AND token = 'Eli8A+RTMrlBrhcLR7WR9oSfElMQFHIRkgALgSHRVko=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}