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SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '12be1b3a4282f04ee61ca3e12e723fad0c9a7f378cb3a9013c9c6c1a48f41884' 
  AND token = 'c/TDBnHAIctS8wR1TIQ5dlxyWyT7dRqFchSsEyE7Uvg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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