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SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '51788d10f2ff225e084cd577c82e50913e132659c30db012fe316e5efae161a5' 
  AND token = '4ouZunr6CM9PZ7PZPkmgiq4i4G4WoB6pKEWBVEhx9V0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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