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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e52d928120ba91dadc0297370f07c07f79dd743e7b1a538a94ad4c6100db3227' 
  AND token = 'eB8xeVr1eavD4scyic6hOJz0Z71GA//PMqXnW/7iCMg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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