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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a73afaa0f033d4558fb2507f7cb851e6a744def7ed12f2d7ad6892c129a80de8' 
  AND token = 'W0ZRxIbiRwQLinyD3EL9frcg+BuhpccMPVnBmHD7K4c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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