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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5013e7a97c5eb10f1c3a5e3cf7226f20172eeb6d351fc4796e176c873b4fb71' 
  AND token = 'vpmRR8l+mqVdDt2fFW5CkFB8XoMrbfRZ2M9VnnDVvT4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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