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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a1621ee6386d0653513ba1248ea5c255c508239c56f7d9be3bac81729d28003d' 
  AND token = 'dA/dwn1igC3PibCcACuns4Gpo0XWNW0zlOralk11Wzg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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