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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4a3a290d4fabf9f1c8808a24a135b58374ab0eea91d2931ed2341a23ac91f610' 
  AND token = '5XXRF3TiHd30ST+v2E9MZxt6dpMccIEPCXV0UY3xGGQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00009

JSON explain

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