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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8f2191995adbd06878cdec675997b421d24ecfc8e8f7d65d8bc6a79173a26d6' 
  AND token = 'mzobyWyPhg8aATFbSwhLrx44cmR2PHY+4YY1SEnPlqY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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