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SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '300b8738ce9576a2222796aef854030ae0c6dec0a8699552468e9e234aba81a2' 
  AND token = '+UhRHT27VGDGKnOMzMM1IrgWe5JMdXsEKiA2kAsIuG0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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